The continual tightening of the world energy supply along with the associated rise in energy costs has brought about a search for alternative energy sources other than the preferred fuels, oils and gas. The most abundant alternative hydrocarbon energy sources in North America are coal, oil shale, and tar sands. These alternative energy sources each have certain problems associated with them. For instance, much of the coal supply in the United States, particularly the eastern regions, are low grade high sulfur coals. The combustion of massive quantities of sulfur is known to cause significant damage to crops, human health, etc. As such, Federal environmental protection laws limit the use of such fuels in large scale operations such as power plants. As the supply of preferred fuels dwindles more and more, economic pressure will force the low grade high sulfur coals into the forefront of the energy market. Oil shale and tar sands have substantial amounts of high molecular weight hydrocarbons, are more difficult to extract and require more processing than crude oil to obtain products similar to present petroleum distillates.
In order to obtain an environmentally clean fuel from coal it has been proposed to pyrolyze it and produce gas which can be cleared of sulfur and transmitted by pipeline to end users, and to produce coal tar liquids which contain aromatic and polynuclear aromatic compounds. We have found that these coal tar liquids are toxic to S. typhimurium and are potentially mutagenic. It would be highly desirable to treat these tars to detoxify them and eliminate or lessen their potential for mutagenicity, thus making them less hazardous to handle and use.
In addition, the coal tars, oil shale and tar sands hydrocarbons require considerable upgrading to be useful as, for example, middle distillates. More efficient and more economical processes for upgrading these hydrocarbons are constantly being sought.